OBJECTIVES This study provided the opportunity to assess the relationship between endothelial vasomotor function and incidence of hypertension in a cohort of postmenopausal women. BACKGROUND Both menopause and hypertension are associated with endothelial dysfunction and are well-known risk factors for atherosclerotic-related disease. METHODS We conducted a prospective cohort study that began in 1996 on 952 apparently healthy postmenopausal women, age 53 +/- 5 years (range 44 to 60 years), with initially normal levels of blood pressure and no history of hypertension. All participants were followed up for a mean period of 3.6 +/- 0.7 years (range 0.5 to 6.9 years). Endothelial function was measured as flow-mediated dilation of the brachial artery using high-resolution ultrasound. RESULTS During follow-up 112 women developed hypertension. The adjusted relative risk for women with flow-mediated dilation of 3.5 or less (lowest quartile) was 5.77 (95% confidence interval 4.34 to 8.10) versus women with flow-mediated dilation of 5.5 or greater (highest quartile, referent). Each one-unit decrease of flow-mediated dilation was associated with a significant 16% (95% confidence interval 12% to 33%) increase in the multiple-adjusted relative risk of incident hypertension. CONCLUSIONS These prospective data indicate a significant increase in the relative risk of hypertension with each unit decrease of flow-mediated dilation that is independent of age and baseline systolic and diastolic pressure values. This could suggest that an impaired endothelial vasomotor function precedes and predicts the future development of hypertension in postmenopausal women. (C) 2004 by the American College of Cardiology Foundation.